2020年9月16日 · Ptolemy's epicyclic, geocentric model, in use until the Renaissance, was very accurate in terms of predicting the positions of planets and the times of eclipses. What it couldn't account for were things like the correlations between apparent size and phase of Venus, or to properly account for the variation in brightness of the planets.

2022年9月28日 · As Rory Alsop points out, the heliocentric model is correct, while the geocentric one is not. Contrary to what Paul Garrett mentions, though, NASA’s model is not geocentric, even though it does allow geocentric coordinates to be determined. I have recently translated Ptolemy’s Almagest to French, including some animations.

2023年5月23日 · The key point is that Venus always goes in a tiny little circle in front of the Sun, in the geocentric model. This was a necessity as they always saw that Venus was close to the Sun, in the morning or after sunset. So when Galileo saw a "full Venus" (implying it was behind the sun) - that broke the model. Here is an illustration:

$\begingroup$ Well, at a simple level, in a geocentric model you're assuming that the frame of the earth is an inertial frame, so using classical dynamics F = ma. But in that frame F doesn't equal ma, there are centrifugal and coriolis forces. The heliocentric model describes that frame as non-inertial, accounting for the extra terms in the ...

2020年7月6日 · Since the geocentric model was totally different from the actual heliocentric model, and the giant transparent spherical shells didn't really exist, there were a lot of problems fitting the directions to various planets at various times predicted by the system with the actual observations of the directions to those planets at those times.

2023年4月29日 · For various reasons, Ptolemy desired to use an epicyclic model. This model allowed him the flexibility to describe a wide range of motions. Ptolemy had inherited a model of the moon's motion from Hipparchus. This had a single epicycle and was quite accurate near full moon and new moon, but not sufficiently accurate at half moon.

2015年2月1日 · In the historic geocentric models, and in particular in the Ptolemaic model, the earth is immobile in the centre of the cosmos, and the sphere of the fixed stars rotates around it once a day, carrying the sun, moon and planets with it.

2021年3月13日 · In the geocentric model, the Sun, the Moon, and the 5 naked-eye planets (Mercury, Venus, Mars, Jupiter, Saturn) all orbited Earth. Today we know that the planets orbit the Sun, and thus they come closer to Earth at certain times than at others. This means that planets are noticeably brighter at opposition than when they're farther away.

2014年4月14日 · Copernicus became to accept the heliocentric model given by Aristarchus due to his study of the Ptolemaic model. His studies showed that planetary motion in a geocentric model was inaccurate. His model, though, was still based on the fact that "heavenly objects" moved in complete circles.

2015年5月21日 · Some of them are stand-ins for the foci of an ellipse in a model made out of perfect circles. And the Sun was actually not the center of the Copernican model, a point near the Sun was. According to Copernicus the Sun was just a decoration which randomly happened to hang around near the center.